Spinning viscose



United States Patent SPINNING VISCOSE Norman Louis Cox, Claymont, and William Dickson Nicoll, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware i No Drawing. Application February 17, 1954 Serial No. 411,029

24 Claims. (Cl. 18-54) This invention relates to the regeneration of cellulose from viscose. More particularly, it relates to a new process for manufacturing regenerated cellulose articles such as filaments or films having improved properties.

It is known that the general strength and quality of viscose yarns are improved through reduction of the primary swelling of the gel fibers. The great importance of the gel swelling factor in viscose spinning operations has attained full recognition only in the last few years (see, for example, U.S. 2,347,883 and 2,347,884). It is now recognized that, to constitute a commercially useful viscose rayon process, the viscose composition and the composition of the sulfuric acid coagulating bath must be so balanced as to permit the production of regenerated cellulose filaments having a gel swelling factor of not more than about 6.5. It has been found that, for a given viscose, yarn properties such as tenacity, elongation, softness, etc., are, as a rule, best when spinning is done at or near the point of minimum gel swelling. It has been found, moreover, that yarn properties are improved through methods designed to reduce the gel swelling factor below the above-mentioned value of 6.5 and that, in general, the greater the reduction, the more marked the improvements. Already the proposed methods of reducing the gel swelling factor include the addition to the coagulating bath of zinc sulfate or of ferrous, manganous, or chromic sulfates (US. Patents 2,364,273; 2,347,883; 2,347,884). While these methods represent valuable advances in the art, further improvements in yarn properties are needed. I

It is well known that unripened viscoses, i.e., viscoses of salt index of about 7 or higher, have not been satisfactory for spinning by the methods currently used in the industry with normally ripened viscoses, i.e., viscoses of salt index of about 5 to 6 or lower. This is attributed to the high primary gel swelling of yarns from green viscoses, even though the high degree of xanthation of green viscoses (which is reflected in proportionately high salt index values) has been thought desirable on theoretical grounds for viscose spinning. A further problem, then, is to make unripened viscose (the so-called green viscose) more amenable to spinning. This is highly desirable since the use of unripened viscose would result in decreasing or eliminating the ripening time now necessary in manufacturing practice. Accordingly, methods for further reducing the gel swelling factor of unripened viscose, and in particular, methods involving further improvements in yarn properties are particularly desirable.

An object of this invention is to provide a process or" manufacturing regenerated cellulose filaments having gel swelling values lower than heretofore attainable by methods known to the art and exhibiting considerably improved yarn properties. Another object is to provide a process whereby unripened viscose can be spun in conventional spinning equipment to give yarn of high quality. A further object is to provide a process of manufacturing regenerated cellulose yarn having entirely novel and desirable properties. Yet a further object is the provision of a method of producing a high-tenacity regenerated cellulose fiber having a non-crenulated surface. Another object is producing very high-strength yarns having smooth (non-crenulated) surfaces with improved soil resistance and abrasion resistance. Other objects appear hereinafter.

These objects are accomplished, in accordance with the invention, by extruding a viscose solution into a coagulating bath comprising an aqueous solution of sulfuric acid and from 1% to 15% of zinc sulfate, the ex truding being conducted in the presence of about 0.01% to about 1%, by weight of one of said solutions, of a diamine soluble in 6% aqueous sodium hydroxide to the extent of at least 0.2% by weight, said diamine containing a total of at least three carbon atoms and having its amino groups attached to aliphatic carbon atoms, the amino groups being separated by a chain of only carbon atoms, any mouovalent substituent on the amino nitrogens being alkyl groups of l to 6 carbon atoms.

The invention will be more clearly understood by re ferring to the examples and discussion which follow. These examples are given for illustrative purposes and are not to be construed in any sense as lirnitative. The numerical values of gel swelling given below for various yarn samples were all determined according to the following procedure:

The gel thread is collected in a monolayer on a bobbin, by manually operating a traverse mechanism with the thread being stretched 100-120% in a secondary (hot dip) bath. The sample is centrifuged (1400 rpm.) for a minute, cut oil, and weighed in a closed bottle. The sample is washed free of acid, dried in an oven at 105 C., and weighed. The ratio of gel weight to cellulose weight (grams of gel per gram of cellulose) is referred to as the gel swelling. Variations may be introduced in the procedure, e.g., in the stretch, spinning speed, or length of bath travel, but these introduce only minor changes in the numerical values of gel swelling. In the case of films, excess bath is removed by blotting with pulp sheet and the gel swelling value is expressed as for filaments.

Another important indication of yarn quality is the factor referred tobelow as D value. This factor relates to the rate of neutralization of the viscose filament in the coagulating and regenerating bath. It is determined by adding to the viscose a suitable indicator, in this case bromocrjesol purple (pH range 5.2-6.8), and observing the distance in inches from the spinneret at which the purple color completely disappears in the traveling filament. This distance is the D value. When films, rather than filaments, are prepared, it is more convenient to express the D value in seconds of time. This is determined by spreading the viscose containing the indicator on a glass plate ot give a layer 0.01 inch in thickness. The plate is immersed in the coagulating bath at 50 C. and the time required for the blue color to disappear from approximately 90% of the film area is determined. This is the D value in seconds. The selected diamines suitable for use in this invention reduce the rate of cose before the gel structure of the filament is permanently set.

In all the examples, the caustic content of the viscose refers to the total alkalinity expressed as sodium hydroxide. It includes free sodium hydroxide and that combined in theform of sodium carbonate, sodium tri'- thiocarbonate, and sodium cellulose xanthate.

3 EXAMPLE I Viscose containing 0.02% by weight of hexamethylenedlamine (0.17 millimole per 100 g. of viscose) is pre pared as follows, using 5% cellulose and 6.5% sodium hydroxide: alkali cellulose aged to get the desired viscose viscosity (30-60 pois es) is xanthated for 3 hours using 43% carbon disulfide (based on the recoverable bone-dry cellulose). The xanthate crumbs are dissolved 1n a solution of sodium hydroxide containing hexamethylenediamine in the amount calculated to give the proportlon mentioned above. After mixing 3 hours at a temperature below 15 C., the freshly prepared viscose is filtered while it is cold, deaerated, and kept at 0 C. until spun, i.e.; it is spun in the unripened state and has a high salt index value, high xanthate sulfur content, and fairly low sodium trithiocarbonate content.

The viscose is converted to a 1100 denier-650 filament yarn by extruding through a spinneret having holes of 0.0025" diameter into a primary coagulating and regenerating bath comprising 8% sulfuric acid, 17% sodium sulfate and 10% Zinc sulfate. The yarn is given a bath travel of 40 inches byusing a roller guide. The apparatus and general procedure used to lead viscose into the bath and to collect the formed thread are essentially the same as those used commercially in the so-called bobbin or spool process. The specific conditions include a bath temperature of 62 C. and the filaments are carried through a secondary bath of 2% sulfuric acid at 95-100" C. The yarn is wound on a bobbin at 28 r.p.m. with a stretch of approximately 110% beyond the pri mary bath. The resulting regenerated gel yarn is Washed free of acid and salt and then processed. The yarns are slashed dry at sufiicient stretch to produce elongation of cords at 10 lb. load of 7-10%. Yarns and cords are tested after conditioning at 76 F. (24.5 C.) and 56% relative humidity for 48 hours.

The properties of the yarn and cord prepared from this viscose are listed in the accompanying table together with those for an unmodified control viscose. It will be seen that the yarn prepared from viscose containing hexamethylenediamine has a lower gel swelling value and a higher D value than the control. Its wet tenacity and elongation are higher than the control. Perhaps the most significant improvement is the substantial increase (0.41 g./den.) in the conditioned cord tenacity. This increase reflects a considerable improvement in the product, particularly for use in tire cords.

The yarns produced by this and the other examples have a number of physical properties which distinguish them sharply from. other regenerated cellulose yarns. These properties are similar to those of the yarns produced through modification of viscose with short-chain quaternary ammonium compounds and selected amines which are described in the Cox U.S. Patents Nos. 2,536,- 014, 2,535,044 and 2,535,045. The most readily apparent modifications are the cross-sections and surface features. For yarns prepared from; unmodified viscose spun into zinc baths, a skin or outer shell which swells to a different extent in water from that of the core is visible. These yarn cross-sections show both deep and shallow crenulations around the contour of the filament. I-lowever, with yarns spun from viscoses modified with diamines as described herein, the boundary between the slon and core is very diffuse; in most; cases the yarn is Three viscoses containing, respectively, per grams of viscose 5.0 millimoles of ethylenediamine (0.3%), 3.4 millimoles of tetramethylenediamine (0.3%), and 3.4 millimoles of N-methyltrimethylenediamine (0.3%), respectively, are prepared using 7% cellulose, 6% sodium hydroxide and 35% carbon disulfide by the method described in Example I. These viscoses, and an unmodified control viscose, are spun into 275 denier-100 filament yarn using a spinneret having holes of 0.0025" diameter and a coagulating bath comprising 7% sulfuric acid, 14% sodium sulfate, and 13% zinc sulfate. The yarns are spun and processed according to the method described in Example I.

From the accompanying table, it will be seen that ad dition of tetramethylenediarnine and N-methyltrimethylenediamine to the viscose has a large effect on the D value, the gel swelling, and the filament stmcture (crosssection). in addition, these filaments have improved yarn and cord properties, similar to those of Example I. Ethylenediamine, on the other hand, does not increase D value or increase gel swelling, and produces a filament of irregular cross-section with reentrant angles.

Table II Modifier D Cross-section value swelling None 3.0 3. 08 Crenulated. Ethylenediamine 3. O 3. 37 Irregular. Tetrnmethylenediamine 10 2. 39 N oncrenulated N-n1ethyltrimethylenediarnine 10 2. 53 Do.

The properties of the yarn produced using the latter two modifiers are comparable to the properties of yarn obtained using hexamethylenediamine.

EXAMPLE III Table III Modifier D Gel Cross-section value swelling None 3. O 3. 19 Orenulated. N,N-dimethylethylenediamine- 15. 0 2. 47 vNonerenulated. N ,N,N,N-tetraethylhexa- 5. O 2. 57 Do.

methylenediamine.

The yarn properties of these filaments show improvements similar to those obtained by the use of hexamethylenediamine.

EXAMPLE IV A viscose containing 0.9 millimole of N,N-diisobntylhexamethylenediamine (0.2%) per 100 grams of viscose is prepared using 7% cellulose, 6% sodium hydroxide and 35% carbon disulfide. This viscose is spun in the bath of Example II, along with an unmodified control viscose. The effects of the diamine added to 5 EXAMPLE VI the viscose on the D value, gel swelling and appearance Cotton linter viscose containing 7% cellulose, 6% of the cross-section of the filament are shown in the total alkali and 35% carbon disulfide is prepared as table below. described in Example II and spun in the unripened state Table IV into a coagulating bath containing 7% sulfuric acid,

14% sodium sulfate and 13% zinc sulfate. In one ex- Modifier D Gel omss secfion perlment (control) no dlamme 18 added to the bath; in m Swelling a second experiment, the bath contains, per 100 grams of bath, 4.9 millimoles (0.5% by weight) of N,N-di- None 3.0 3.18 Granulated. methyltlimethylenediamine; in a third experiment, the hlgg gg Ntmcrenulatedbath contains, per 100 grams of bath, 8.6 millimoles 1% by weight) of hexamethylenediamine. The table below shows the changes in D value and gel swelling In contrasi i the preceidmg i It Should b6 factor produced by the addition of these diamines to noted that diamines not falling within the operable class the spi g bath defined above, such as di(p-aminophenyl)methane or N- dodecyltrimethylenediamine, have substantially no eifect Table VI on the gel swelling, D value and filament structure.

Diamine "1) Gel EXAMPLE V value swelling This example describes a series of film casting experiments with viscoses containing various diamines of the fi gf lmmeth lenediamme 3-2 2-3 general class defined above. It has been found that the nsxsmeth ignedismin e 'IIIIIIIIII 410 311 data obtained on films with respect to the effect of the amine modifiers on gel swelling and D value are equally applicable to filaments. In other words, if a given dicontrast, addition of 1% of ethylene diamine to the amine has a beneficial effect on the D value and gel P mmg bath produced no increase in D value and swelling when tested by the film-casting technique, it no app decrease in the gel swelling factorwill have a similar effect on filaments spun from the h re n be used n the process of this invention any modified vi o e, primary, secondary or tertiary diamine which is soluble In all the experiments tabulated below, the viscose is III 6% aqueous Sodium yfi n t0 the eXteHt of at prepared using 7% cellulose, 6% sodium hydroxide and 5 y g I requllement insures 80111- 35% carbon disulfide, based on the bone-dry cellulose. l y 0f the diamille 111 1150056, Which is essential Since Films of 10 or 15 mil thickness a spread f th 1t has been found that diamines which arenot completely unripened viscose on a glass plate with a doctor knife and dlssolvedi Whlch e wholly or Partially P103911t as immersed into a coagulating bath at 50 C. In all cases a dispel'slofl rather than a Solution, give unsatisexcept one, the coagulating bath contains 8% sulfuric factory results f the P p of this invention hi acid, 23% sodium ulfate and 4% zinc lf t Th requirement operates also when the diamine is used in exception is run 8, using 1,4-cyclohexanediamine, in the coagulating bath, since it should be noted that some which a bath of 6% sulfuric acid, 23% sodium ulfate diamines are practically insoluble in the normal coagulatand 4% zinc sulfate is used. The D values, expressed mg baths, -g-, baths containing 13% or more of Sodium in seconds rather than inches, as discussed above, and Sulfate, in spite of the fact that the baths are acidic. the gel swelling ratios are shown in the table below. Dlamines soluble to the extent of at least 0.2% in 6% Table V Amount D value (seconds) G 1 e Run Diamine swelling Milliratio, moles per Weight Control Modified modified 100 g. of percent viscose viscose viscose VISCOSG 1..-- Trhnethylenediamlne"; 4.0 0.3 16 25 0.56 2.--. Tetramethylenediamina. 2.6 0.23 16 31 0.68 3.-.. N-methyltrlmethylenediamine. 2.6 0.23 16 25 0.65 4.... N,N-dimethylethylenediamlne. 3.4 0.3 16 23 0.62 5...- Piperazine 3.5 0.3 15 16 0.88 6 N,N-dimethyltrimethylenediamine. 3.0 0.3 16 20 0. 74 7-- Hexamethylonediamine 1.3 0.16 15 0.65 8 1,4-cyclohexanediamine 2.6 0.3 20 28 0.88 9- 3-methoxyhexamethylenediamlne 2.0 0.3 32 33 0.73 10..- 3-dimethylaminohexamethylenediamine 1.9 0.3 32 33 0.76 1l 4,4-dimethylhexamcthylenediamine 1.4 0.22 17 0.85 12--- N,N-diethy1-l,4-cyclohexanedlamine 2.2 0.5 17 45 0.72 13 3 ethoxyethoxyhexamethylenediamine 1.5 0.3 32 55 0.63 14- N,N,N,N-tetraethylhexamethylenediamine 1.3 0.3 17 45 0.63 15..- N,N-diisobutylhexamethylenedlamine 2.2 0.5 15 40 0.73

In each of the experiments described above the consodium hydroxide have generally been found to be also trol gel swelling ratio is 1.0, no reduction being involved soluble in coagulating baths. and the gel swelling ratio, the ratio of the gel swelling In addition to the solubility requirement, the suitable factor of the modified sample to that of the unmodified, indicates the reduction gained in gel swelling by use of the specific modifiers of this invention.

In contrast with the results shown, the use of diamines not belonging to the operable class such as ethylenediamines should contain at least three carbon atoms in the molecule. The amino groups should be attached to aliphatic carbon atoms only, that is, to carbon atoms which are not part of an aromatic nucleus or of a heterocyclic nucleus aromatic in character, and no atoms other than carbon should be present in the chain separating the amino groups, although other groups such as alkoxy, heterocyclic, aromatic or dialkylarnino groups may be attached as side chains to these carbon atoms. The amino nitrogen atoms are separated by at least two carbon atoms. Finally, it has'been found that the monovalent substituents, if any, on one or both of the nitrogen atoms, should be alkyl, including cycloalkyl, groups of 1 to 6 carbon atoms.

The preferred diamines for use in the process of this invention are the wholly aliphatic, including cycloaliphatic diamines which contain only carbon and hydrogen besides the two amino nitrogens and which have a total number of carbon atoms between 4 and 14, inclusive, in addition to fulfilling the other requirements discussed above. Still more preferred are the polymethylenediamines of 4 to 14 total carbon atoms having from 4 to 8 methylene groups between the amino groups, and their N-alkyl substituted derivatives where the N-alkyl groups have from 1 to 4 carbon atoms, inclusive. In addition to the several diamines disclosed in the foregoing examples, other suitable compounds include pentamethylenediamine, octamethylenediamine, N cyc'lohexyltetramethylenediamine, N,N-diallylhexamethylenediamine, N-methylnonamethylenediamine, N-hexyltrimethylenediamine, N,N-dimethylpiperazine, N-butylhexamethylenediamine and the like. Mixtures of two or more diamines can be used.

The diamine may be used either in the viscose or in the coagulating bath or both, but much better results are in general obtained when it is used in the viscose, and this embodiment of the invention is therefore the preferred one. For effective results, it is desirable that the solvent for the amine (viscose or coagulating bath) contain at least 0.01% of the diamine by weight. It is in general unnecessary to use more than 1% by weight of the modifying agent, a generally useful range being 0.02-0.5%. When the diamine is used in the coagulating bath, it is in general desirable to use more of it than when it is present in the viscose, a suitable range of concentration in the bath being 0.2-1%. An optimum concentration for any given agent, whether in the viscose or in the bath, depends on its effectiveness and on its molecular weight. Perhaps a preferable manner of expressing the concentration is in terms of millimoles of diamine per 100 grams of solvent. Between 0.1 and 10 millimoles of diamine per 100 grams of viscose is a suitable range of proportions, although more can be used if desired and if the diamine is sufliciently soluble. In the coagulating bath, there can be used between 1 and 15 millimoles of diamine per 100 grams of bath. The optimum amount of diamine to be used also depends to some extent on process variables such as the spinning speed, since at the high spinning speeds used in industrial practice less agent is desired than at lower speeds, for the reason that the rate of neutralization of the filament should be retarded only to the extent compatible with complete coagulation during the short time the filament is in contact with the coagulating bath. Determination of the optimum concentration of the amino compound is a matter of simple experimentation for those skilled in the art.

The viscose used in the process of the invention may be of a variety of types; for example, it may be from wood pulp, cotton linters, mixtures of the two, or even other types of cellulose. The composition of the viscose may also be varied widely. For example, it may have a cellulose content of from 4 to 10%, or even more, and an alkali content of from 4 to 8% or more. The standard viscoses of the industry, i.e., those having between 5 and 7% cellulose and between 4 and 6% alkali, are preferably used. The amount of carbon disulfide used in the xanthation can be from 25-5 0% (based on the recoverable bonedry cellulose). It has been found that higher than normal xanthate sulfur contents (higher salt indices) can be used in the viscose when the diamines described herein from 30 C. to 70 C. or higher.

are added and there {appears to be an advantage in stretchability and level of yarn properties if salt indices higher than 5 are used. It is necessary to use 30% or greater amounts of carbon disulfide to obtain salt indices of 5 or over in unripened viscoses. Thus, one of the chief advantages of the invention is that unripened or partially ripened viscoses may be used, with the result that the ripening time and space now required in viscose plants may be eliminated or substantially reduced. However, notable improvements in yarn quality are also obtained with normally ripened viscose, thus making the process directly applicable to existing plant practice. The method of preparing the viscose is not critical. The viscose may be prepared by conventional methods or by the so-called split-xanthation techniques disclosed in copending application Ser. No. 351,592, filed April 28, 1953, now Patent No. 2,801,998.

The spinning baths suitable for use in the invention contain sulfuric acid, usually sodium sulfate, and zinc sulfate. Zinc sulfate is an essential component of the spinning bath since, in its absence, or if it is present in insufficient amount, the amine compounds have no effect on spinning and yarn properties. If desired, additional salts of divalent metals known to reinforce or supplement the action of zinc sulfate may be used, such as ferrous sulfate, manganese sulfate, magnesium sulfate, nickel sulfate, or chromic sulfate, preferably ferrous sulfate. When one or any of these supplementary metal salts are used, smaller amounts of zinc sulfate are required. Preferably, the spinning bath contains from 4 to 12% of sulfuric acid, from 13 to 25% of sodium sulfate, and from 2 to 15% of zinc sulfate; if ferrous sulfate is to be used, 1 to about 5% is normally added. The optimum quantity of Zinc sulfate for industrial practiceappears to be 3 to 10%; however, 15% Zinc sulfate is quite satisfactory for reducing gel swelling and improving yarn properties. With the addition of diamines to the baths, it is possible to obtain excellent yarns in the upper range of bath acidity under which conditions normal, unmodified viscoses give yarns of decreased quality. The tem-- perature range of best spinnability is from 40 C. to 65 C. On the basis of available data, it is desirable to have the bath acidity and temperatures as low as is practical for a given spinning speed in order to get optimum filament structure and yarn properties. Each of the above concentrations should be adjusted to each other and to the composition of the viscose. It is desirable to use as high a total solids content as possible in the coagulating bath to give the highest degree of gel shrinkage and improved stretchability.

The viscose filaments may be extruded at temperatures of 15 C. to 30 C. or the viscose may be heated immediately prior to extrusion to temperatures ranging The filaments may be given a long travel of 130 to 250 inches in the primary bath by means of a multiple roller setup which gradually applies tension to the traveling filaments and thereby orients them while they are still plastic. The preferred method, however,.is to apply a part or all of the stretch beyond the primary bath in a secondary bath or to use a combination of air and hot-bath stretch. The secondary bath may consist simply of water or of dilute (1% to 3%) sulfuric acid, or it may have the same composition as the coagulating bath but a greater dilution, e.g., onefourth of the concentration of the coagulating bath. The temperature of the secondary bath is preferably between 50 C. and C. Stretches of 80% to are preferred for producing high-tenacity yarn and 20% to 30% for textile type yarns. The bobbin process has been used in the example, but it is immaterial whether spinning is by bobbin, bucket, or continuous process. The yarn cake is washed free of acid and salt, then dried under tension. If preferred, it may betwisteror slasherdried to enable the dry elongation of the finished product to be controlled. When using the two-bath spinning ystem, the P ef d pr cedure s o d aw off the fr hly 9 coagulated gel yarn with a feed-wheel speed equal to or less than the jet velocity and to apply all of the stretch between positively driven rollers traveling at difierent speeds. The thread can be given a travel of to 50 inches in the secondary bath of hot water or dilute bath. As mentioned above, the amount of stretch applied depends on the properties desired for the yarn.

Spinning may be carried out with the aid of spinning tubes such as described in Millhiser US. Patent 2,440,057 or in Drisch et al. US. Patent 2,511,699. These tubes of relatively small diameter and of substantial length confine the bath and filaments in their critical stage of formation so that no substantial tension is imposed on the filaments because the speed of the concurrent bath flow is maintained only slightly below the speed of the filament bundle passing through the tube. It is thus possible to increase materially the rate of spinning over methods earlier described without substantial sacrifice in the desirable properties set forth above.

The novel and improved yarns obtainable through the process of this invention have substantially improved physical properties such as wet tenacities and can, in general, be used instead of regular regenerated cellulose fibers for any purpose where the latter are finding applications, more particularly in the textile and tire cord industries. The invention is generally applicable to the preparation of filaments, yarns, films, caps, bands, ribbons, and other structures of regenerated cellulose. For convenience it has been discussed with particular reference to the production of viscose rayon yarn; other articles can be made using the information given to improve properties.

This is a continuation-in-part of our copending application Serial Number 228,980, filed May 29, 1951.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the claims.

We claim:

1. A method of producing regenerated cellulosic structures which comprises extruding a viscose solution in a coagulating bath comprising an aqueous solution of sulfuric acid containing from about 1% to about zinc sulfate, said coagulating being conducted in the presence of about 0.01% to about 1.0%, by weight of one of said solutions, of an aliphatic amine containing two amino nitrogen atoms separated by at least two carbon atoms, containing a total of at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms and the said amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

2. A method of producing regenerated cellulosic structures which comprises extruding viscose in an aqueous sulfuric acid coagulating bath containing from about 1% to about 15 zinc sulfate together with about 0.01% to about 1.0% by weight of said bath of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing a total of at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and the said aliphatic amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

3. A process in accordance with claim 2 in which the said structures are passed into a second bath and subjected to a stretching treatment in said second bath.

4. A process in accordance with claim 2 wherein said amine is used in amounts of about 0.2% to about 1.0%.

5. A method of producing regenerated cellulosic structures which comprises extmding viscose in an aqueous sulfuric acid coagulating bath containing from about 1% to about 15% zinc sulfate, the said viscose containing about 0.01% to about 1.0% by weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing a total of at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and the said aliphatic amine being soluble to the extent of at least 0.2%by weight in 6% aqueous sodium hydroxide.

6. A process in accordance with claim 5 wherein said structures are passed into a second bath and subjected to a stretching treatment in said second bath.

7. A process in accordance with claim 5 wherein said amine is used in amounts of about 0.02% to about 0.5%.

8. An aqueous sulfuric acid coagulating bath for the preparation of regenerated cellulosic structures from viscose, said bath comprising an aqueous solution of sulfuric acid with from about 1% to about 15% zinc sulfate with about 0.01% to about 1.0% by weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and the said aliphatic amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

9. A bath in accordance with claim 8 which contains about 0.2% to about 1.0% of said amine.

10. A bath in accordance with clain 8 which contains about 13% to about 25% sodium sulfate.

11. Viscose containing about 0.01% to about 1.0% by Weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and. the said aliphatic amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

12. Viscose having a salt index of at least 5 and containing about 0.1% to about 1.0% by weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and the said aliphatic amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

13. Viscose containing 4% to 10% cellulose combined as sodium cellulose xanthate with from 25% to 50% carbon disulfide, 4% to 8% of sodium hydroxide and about 0.01% to about 1.0% by weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing at least three carbon atoms, any monovalent substituent on an amino nitrogen atom containing no more than 6 carbon atoms, and the said aliphatic amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

14. A method in accordance with claim 1 wherein said viscose is unripened viscose.

15. A method in accordance with claim 2 wherein said viscose is unripened viscose.

16. A method in accordance with claim 5 wherein said viscose is unripened viscose.

17. The composition in accordance with claim 11 in which said viscose is unripened viscose.

18. The composition in accordance with claim 12 in which said viscose is unripened viscose.

19. The composition in accordance with claim 13 in which said viscose is unripened viscose.

20. Viscose containing about 0.01% to about 1.0% by weight of an aliphatic amine containing only two amino nitrogen atoms separated by at least two carbon atoms, containing at least three but no more than 14 carbon atoms and being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

21. Viscose in accordance with claim 20 in which the 11 said amines are polymethylenediamines having from 4 to 14 carbon atoms and having 4 to 8 methylene groups between the amino nitrogen atoms, any alkyl groups attached to the. said amino nitrogen atoms having from 1 to 4 carbon atoms.

22. A process in accordance with claim 1 wherein said amine is added to said viscose in an amount within the said percentages.

23. A process in accordance with claim 1 wherein said amine is added to the said aqueous solution in an amount within the said percentages.

24. A method of producing regenerated cellulosic structures which comprises extruding a viscose solution in a coagulating bath comprising an aqueous solution of sulfuric acid containing from about 1% to about 15% zinc sulfate, said coagulating being conducted in the presence I?! amino nitrogen atoms. separated by at least two carbon atoms, containing a total of at least three carbon atoms, any monova'lent 'subst-ituent on an amino nirogen atom containing no more than 6 carbon atoms and the said amine being soluble to the extent of at least 0.2% by weight in 6% aqueous sodium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,300,589 Nelles Nov. 3, 1942 2,319,199 Tallis Feb. 23, 1943 2,432,085 Bley Dec. 9, 1947 2,451,558 Schlosser et al. Oct. 19, 1948 2,481,692 Schlosser et al. Sept. 13, 1949 2,481,693 Schlosser et a1. Sept. 13, 1949 2,784,107 Tallis et a1. Mar. 5, 1957 2,792,279 Lytton May 14,1957 2,792,281

Castellan May 14, 1957' 

2. A METHOD OF PRODUCING REGENERATED CELLULOSIC STRUCTURES WHICH COMPRISES EXTRUDING A VISCOSE SOLUTION IN A COAGULATING BATH COMPRISING AN AQUEOUS SOLUTION OF SULFURIC ACID CONTAINING FROM ABOUT 1% TO ABOUT 15% ZINC SULFATE, SAID COAGULATING BEING CONDUCTED IN THE PRESENCE OF ABOUT
 0. 01% TO ABOUT 1.0%, BY WEIGHT OF ONE OF SAID SOLUTIONS, OF AN ALIPHATIC AMINE CONTAINING TWO AMINO NITROGEN ATOLS SEPARATED BY AT LEAST TWO CARBON ATOMS, CONTAINING A TOTAL OF AT LEAST THREE CARBON ATOMS, ANY MONOVALENT SUBSTITUENT ON AN AMINO NITROGEN ATOM CONTAINING NO MORE THAN 6 CARBON ATOMS AND THE SAID AMINE BEING SOLUBLE TO THE EXTENT OF AT LEAST
 0. 2% BY WEIGHT IN 6% AQUEOUS SODIUM HYDROXIDE. 